It is not required to be transferred through a Federal Firearms License Dealer with all the federal paperwork like its finished counterpart, the completely finished lower receiver. These factors make for easy purchasing for home gunsmiths and hobbyists for personal use.

As long as the following laws are met there are no problems:

You can legally own the firearm in question in the state in which you live

You are building the firearm for your personal use and for yourself only.

It is a good idea to mark your firearm somehow so that should it ever be lost or stolen you have a way to identify it and report its loss to your local law enforcement. Please check your local and state laws.